We plan to continue our exploration of the scope and mechanism of a type of chain-lengthening process exemplified first in the biosynthesis of alpha-ketoglutarate from oxaloacetate in the Krebs cycle, and shown more recently to be a key feature of the biosynthesis of a variety of amino acids which are immediate precursors of the mustard oil glucosides (glucosinolates) occurring in the Cruciferae and other plants. There are clear indications that the enzyme systems involved may constitute a large group with much structural diversity but common stereochemical features and, possibly, other mechanistic similarities. We intend also to continue work on related aspects of amino acid metabolism. Our methods involve synthesis of isotopically-labeled amino acid homologs of various chain lengths and testing them as precursors of glucoinolates. Tests of proton migration in the isomerization step involve the synthesis of substrates labeled with tritium at specific sites. In addition, the chiralty of intermediate steps in the pathways of catabolism is being explored by use of chirally labeled amino acids (employing both 13C and 2H) and the techniques of proton and 13C nmr.